Introduction

Advanced oxidation process (AOP) is a new form of the advanced treatment of wastewater that has received much attention in recent years and is characterized by strong oxidation, rapid degradation, mild reaction conditions, and more thorough degradation of pollutants (Liu et al. 2020b; Sun et al. 2017, Wang and Wang 2021). Common AOPs include photocatalysis (Lai et al. 2019b; Li et al. 2018; Qin et al. 2019; Zhou et al. 2018), Fenton oxidation (Lai et al. 2019a), ozone oxidation (Levanov et al. 2019), persulfate activation (Li et al. 2022; Zeng et al. 2021; Zhu et al. 2023), and electrochemical oxidation (Zhang et al. 2019b). However, most of the oxidation methods in AOPs require large amounts of energy, complex operation, high cost, and harsh reaction conditions. Among them, the Fenton reaction process has a very wide pH range (2-4). The pH of the solution is too high or too low to effectively treat organic pollutants in wastewater. In contrast, PS is more friendly to the environment, easier to transport and store, and more stable in conventional environments. The PS can absorb energy or obtain an electron to generate SO4•−, which can react further with water or hydroxide ions to generate •OH. In conventional methods, heat (Fan et al. 2015; Milh et al. 2021; Oh et al. 2009), UV-visible light (Ao et al. 2019; Lu et al. 2017), ultrasound (Monteagudo et al. 2018; Nasseri et al. 2017), transition metal ions (Fang et al. 2021; Wacławek et al. 2017; Wang et al. 2021a; Wei et al. 2016), and alkali can effectively activate PS to produce sulfate radical (SO4•−) and hydroxyl radical (•OH). However, the several physical methods mentioned above generate high energy consumption. Transition metal ions need complex subsequent treatment to avoid secondary contamination. Alkali activation method needs to adjust the pH value, which is a risk of equipment corrosion (Fu et al. 2021; Shi et al. 2017; Wu et al. 2018). Therefore, it is necessary to explore more efficient and green activation methods.

Carbon materials have broad applications in the field of catalysis due to their unique nanostructures, good electrical conductivity, chemical stability, and strong adsorption capabilities (Chen et al. 2021; Yu et al. 2020; Zhou et al. 2019). Carbon materials have been proven to be effective in activating PS by replacing various metals and metal oxides in various chemical processes. (Duan et al. 2016) found that phenol can be completely degraded after 150 min of reaction in the reduced graphene oxide rGO-900/PMS system. (Cheng et al. 2017) discovered that carbon nanotubes (CNTs) materials can effectively activate PS to produce singlet oxygen, thereby effectively degrading various pollutants. (Forouzesh et al. 2019) reported that oxidative degradation and adsorption jointly acted on the removal of metronidazole in the granular activated carbon (GAC)/PDS system, and PS efficiency was much higher than that of H2O2. However, the carbon-based materials mentioned above are generally expensive. In recent years, BC has been considered as an efficient carbon-based material for degrading organic pollutants due to its low cost, availability, ease of preparation, and recyclability of resources. It can be obtained by the pyrolysis of biomass feedstock under high temperatures and low oxygen conditions. Its morphological structures and physicochemical properties vary depending on the biomass and the pyrolysis process (Tag et al. 2016). Among them, metal-free BC materials exhibit non-metallic leaching properties, acid and alkali resistance, biocompatibility, recyclability and adaptability, and are promising and efficient catalysts (Chen et al. 2021; Yu et al. 2020). A series of studies have been undertaken on the activation performance of PS by using different types of metal-free biochar, such as sludge biochar (Huang et al. 2018, Wang and Wang 2019, Wu et al. 2021b, Yin et al. 2019), straw biochar (Duan et al. 2022; Feng et al. 2022; Tang et al. 2023; Wang et al. 2019a), wood biochar (He et al. 2019; Ouyang et al. 2019), algae biochar (Ho et al. 2019), shell biochar (Liang et al. 2019), and some biochar from waste (Chen et al. 2023; Zhao et al. 2022). BC from different biomass sources possesses different elemental compositions, surface structural properties, and redox capacities, which in turn affect their performance in PS activation efficiency. Thus, it is necessary to investigate the impact of the inherent properties of biomass on the performance of BC.

Microorganisms are the most biodiversity organisms on earth. They perform an essential role in the biosphere and provide mankind with numerous untapped resources. Especially bacteria have great potential for bio-decontamination in environmental pollution management (Timmis and Hallsworth 2022). Microorganisms can be used to degrade organic matters such as plastics (Zeenat et al. 2021) and toluene (Yan et al. 2020), and can also treat phosphates in industrial wastewater (Si et al. 2021) and sulfur-containing waste gasses, and can also help improve soil (Sanz et al. 2022). Recent years, the use of microorganisms in new directions has been studied. Liu et al. (Liu et al. 2021) investigated the different antioxidant capacities of Lactobacillus plantarum by crushing it with various methods such as high-pressure treatment (HIP), lysozyme combined with ultrasonic treatment (LCU), and freeze–thaw treatment (FAT). (Dong et al. 2022) investigated the effect of different forms of phosphate-solubilizing bacteria-Paenibacillus xylanexedens (bacterial supernatant, bacteria, broken bacteria) on Chlorella pyrenoidosa, providing a new approach to the treatment of wastewater. (Zhang et al. 2019a, 2021, 2022b) prepared novel and effective oxygen reduction reaction (ORR) electrocatalysts by crushing Shewanella cells through carbonization, electrostatic spinning-carbonization, and hydrogen reduction techniques. Based on the above research, we consider whether bacteria can be used as raw materials for the preparation of BC.

Using bacteria as precursor materials for the preparation of biochar, large surface areas and potentially controllable pore structures in carbon materials can be formed due to various highly porous cellular structures possessed by bacterial cells (Wei et al. 2015a, 2015b). Meanwhile, carbon materials with specific functions can be obtained from bacteria with the appropriate processing method (Guo et al. 2015). For example, (Wei et al. 2015b) synthesized heterogeneous carbon materials with nitrogen and phosphorus doping by direct carbonization using Escherichia coli (E.coli) as a precursor, and (Zhu et al. 2013) synthesized N-doped nanospheric particles with Bacillus subtilis by ion heating method. The electrochemically active bacterium, Shewanella oneidensis MR-1, is widely distributed in nature, and has low nutrient requirements, and can survive in common media (Yang et al. 2017; Zhang et al. 2009, 2022b). MR-1, as a Gram-negative facultatively anaerobic bacteria, consists of peptidoglycan, phospholipids, lipoproteins, and lipopolysaccharides, which can provide abundant heteroatoms for carbon materials. In addition, the outer membrane of MR-1 contains cytochrome c, a heme protein containing iron porphyrins, which is capable of electron transfer (Wu et al. 2023). (Hartshorne et al. 2007) reported that the iron porphyrin (Fe-N4) on the outer membrane of MR-1 can be found to be transformed into Fe-Nx-C type active sites for ORR by pyrolysis. Therefore, in this work, Shewanella oneidensis MR-1 was first used as the precursor material of BC to evaluate the degradation effect of activated persulfate on organic pollutants.

Materials and methods

Experimental materials

Shewanella MR-1 was provided by the laboratory of the Guangdong University of Technology. rhodamine B (RhB), potassium persulfate (PS), hydrochloric acid (HCl), and sodium hydroxide (NaOH) were obtained from Yung Man Biotech Co., Ltd. (Guangzhou China); methanol (MeOH, 99.0%), tert-butyl-alcohol (TBA, 99.0%), and sodium azide (NaN3) were purchased from Sinopharm Chemical Reagent Co., Ltd. All chemicals utilized in this study were analytical grade.

Experimental procedure

The frozen MR-1 strain was first activated with beef paste peptone solid plate medium. Single colonies were then selected for enrichment in Luria–Bertani liquid medium (30°C, 150 rpm·min−1), placed in a shaker and incubated aerobically for about 24 h to obtain the mother liquor.

The cultured MR-1 bacterial solution was centrifuged at 4℃ (6000 r·min−1, 10 min) to settle the bacterium, removed the supernatant, and washed repeatedly with sterile saline more than three times to remove the residual medium, and then collected and dried at 60°C for 8 h in vacuum oven. Finally, solid particles/powder of MR-1 bacteria were collected and stored in a refrigerator at - 4℃. Subsequently, the dried MR-1 strain powder was placed in tube furnace (OTF-1200X, KeJing) for calcination. The temperature was raised to 700℃ for 4 h at a heating rate of 5℃·min−1 under the protection of nitrogen (N2). After completion of the pyrolysis, the MR-1 powder sample was removed and washed several times with hydrochloric acid and then deionized water to neutralize to ensure complete removal of any residual inorganic ions. The washed samples were then dried in an oven at 65°C for 12 h to obtain MR-1 after carbonization (MBC).

RhB degradation experiments were performed in a brown conical flask with the beaker magnetically stirred (400 rpm) at ambient temperature. The initial pH of the reaction solution was adjustable using 0.1 M H2SO4 and 0.1 M NaOH. During the degradation of the system, a certain amount of MBC catalyst (0.2 g/L, 0.4 g/L, 0.6 g/L, 0.8 g/L) was added to 10 mg/L of RhB solution. Different concentrations of PS (2 mM, 4 mM, 6 mM, 8 mM) in the mixed solution were added to initiate the degradation reaction. The whole experiment was carried out under the condition of avoiding light. To measure the absorbance, the solution was collected at predetermined intervals and filtered through 0.22 µm filter. To evaluate the stability and reusability of the MBC, the reacted BC was washed repeatedly with ultrapure water and ethanol by means of filtration, followed by drying at 60°C, and then used for the next round of degradation experiments. The radical species in the MBC/PS system were determined using methanol (MeOH), tert-butyl alcohol (TBA), and sodium azide (NaN3) as quenching agents. All trials were done in three parallel groups.

Analytical methods

The morphological changes before and after MBC reaction and the composition of micro-elements were analyzed by scanning electron microscopy (SEM, FEI INSPECT F50) and Energy Dispersive Spectrometer (EDS, Hitachi SU8100), respectively. Functional groups on the material surface were explored using a Fourier transform infrared spectrophotometer (FTIR, Nicolet 6700). A D8 Advance X-ray powder diffractometer (Bruker) was applied to study the crystalline structure of the BC material. The specific surface area and pore size distribution of the samples were determined by N2 adsorption–desorption isotherms using a Brunauer-Emmett-Teller (BET, Micromeritics, 3-flex) at 77 K. RhB concentration was determined by ultraviolet spectrophotometry (UV-2600, Shimadzu). The EPR analysis was carried out with a Bruker EMXplus-10/12 spectrometer.

The degradation process of RhB in the MBC/PS system conforms to the pseudo-first-order kinetic model (Zhu et al. 2018b).

$$\mathrm{ln\;}C/{C}_{0}=-{k}_{obs}t$$

where C0 (mg/L) is initial RhB concentration, C (mg/L) is the concentration of RhB at a given time (min), and kobs are the estimated pseudo-first-order rate constant (min−1).

Results and discussion

Characterization of MBC

The morphology of S. oneidensis MR-1 and MBC were analyzed by SEM to compare the changes of pure bacteria and MBC before and after the reaction. As shown in Fig. 1a, MR-1 showed a rod-like shape with rough surface, but the bacteria were relatively intact, and the length of the bacteria was about 2–3 μm. It can be clearly seen from Fig. 1b-c that the morphology of MBC obtained by high-temperature calcination of MR-1 has changed greatly, showing irregular block structure and rich pore structure. Meanwhile, significant morphological differences are not observed for the MBC before and after the reaction. The mass ratio of MBC before and after heating at 700 °C for 4 h in a muffle furnace was used to calculate the ash content of MBC was 28.81% (Wang et al. 2019b). EDS energy spectrum in Fig. 1d showed that MBC contains the other elements of Na, K, P, Zn, Mg, Ca, and Al and the main elements of C, N, and O. Trace Fe was also found probably due to the existence of iron porphyrin on the outer membrane of MR-1. By comparing the specific surface area of MBC before and after the reaction, it can be observed that the specific surface area of the sample increased from 3.9933 to 5.0058 m2g−1 (Fig. 2a-b), which was estimated by the Brunauere-Emmette-Teller (BET) equation. It may indicate that MBC has no adsorption effect on RhB. Adsorption often shields the active center and hinders the electron transport process, thus affecting the catalytic performance (Liu et al. 2020a). Calculated by the Barrette-Joynere-Halenda (BJH) equation, the pore volume and average pore size of the MBC before and after the reaction were 0.0116 cm3g−1, 0.0118 cm3g−1, 11.5977 nm, and 9.3968 nm, respectively. It can be noticed that the isotherms of adsorption and desorption of MBC were not closed to result in a non-closed hysteresis loop, which can indicate the microporous structure of MBC. Furthermore, the average pore radius centered at 2 nm (Fig. 2c) could also indicate a homogeneous microporous structure in the MBC. It was reported that the uniform porous structure of BC can offer more active sites to favor the activation of PS (Zhao et al. 2022).

Fig. 1
figure 1

SEM images of MR-1 (a), before (b) and after the reaction of MBC (c), and EDS spectra of MBC (d)

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Fig. 2
figure 2

BET before the reaction (a) and after the reaction (b), pore size distribution of MBC (c)

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The XPS spectra of Fig. 3 provide a simple qualitative analysis of the main constituent elements of MBC. The wide-survey XPS spectra revealed three distinct distinctive peaks of C 1 s (284.30 eV, 47.03 at. %), N 1 s (399.18 eV, 5.49 at. %), and O 1 s (531.45 eV, 6.89 at. %). The C 1 s spectrum is shown in Fig. 3a and could be considered as the contents of C–C/C = C (284.8 eV), C-O (285.92 eV), and O-C = O (288.75 eV) (Kong et al. 2016; Shi et al. 2017; Wu et al. 2021b). The presence of elemental nitrogen can be divided into three forms (Fig. 3b), namely, pyridinic N (397.43 eV), graphitic N (399.71 eV), and nitric oxide (403.27 eV) (Wang et al. 2021b; Wu et al. 2021b). The presence of N and other heteroatoms could disrupt the original chemical inertness of the carbon layer, producing more defects on the surface and offering more reaction sites for the activation of PS (Chen et al. 2021). The O 1 s of Fig. 3c was fitted by three peaks. The first one was located in the lower binding energy (530.3 eV) and can be attributed to O2−. Two other components were identified as OH-/C–O–C (532.06 eV) and C = O (534.48 eV), respectively (Kong et al. 2016; Wu et al. 2022c; Zhou et al. 2020). Zhao et al. showed that the surface oxygen-containing groups of BC materials, such as carbonyl (C = O), carboxyl (-COOH), and hydroxyl (C-OH) groups, may benefit the catalytic performance of BC (Zhao et al. 2020).

Fig. 3
figure 3

XPS spectrum of full-scan (a), C1s (b), N1s (c), and O1s (d) of MBC

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The X-ray diffraction patterns of the samples are shown in Fig. 4a. A broad diffraction peak can be observed at 2θ = 26°, which probably corresponds to the (002) graphitic carbon plane. The broader peak appearing at 2θ = 43° can correspond to the (100) plane of crystalline carbon. It indicated that all samples are amorphous and have an amorphous graphitic carbon structure (Wang et al. 2019a). The diffraction peak at 2θ = 26° indicated parallel stacking and interconnection between the various parts of the graphite layers in carbon materials. The diffraction peak at 2θ = 43° showed that sp2 hybridized carbon atoms interact with each other in the carbon material to create a hexagonal lattice structure (Wang et al. 2021b). In addition, the diffraction peak that appears near 20° represents the graphitized structure (Ding et al. 2021). Two more pronounced diffraction peaks appear near 2θ = 32°, corresponding to the diffraction peaks of (112) and (202) crystal planes of glucuronamide (C6H11NO6) (Qiao et al. 2016). These diffraction peaks may be due to the carbonization of organic components such as peptidoglycan, lipids, and proteins on the bacterial cell wall (Dik et al. 2018). Fig. 4a revealed that there was no significant variation in the BC samples before and after the reaction, which can indicate the stability of MBC.

Fig. 4
figure 4

XRD (a) and FTIR spectra (b) of MBC before and after the reaction

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FTIR spectroscopy was used to compare the differences in the structure and surface groups of MBC before and after the reaction. As observed in Fig. 4b, five distinct peaks of 3425, 2928, 1700, 1533, and 1104 cm−1 appeared in the spectra. The peak around 3425 cm−1 is allocated to the stretching vibrations of -OH in phenol functional groups and carboxyl groups (Zhu et al. 2018b). This peak is closely related to the one at 1104 cm−1, due to the symmetric C-O or C-O-C stretching. A peak at 1700 cm−1 is caused by the C = O groups (Avramiotis et al. 2021; Guo et al. 2021; Liu et al. 2022b). The bands at 2928 cm−1 and 1533 cm−1 stand for the stretching vibration of -CH2- and C = C stretching, respectively (Liu et al. 2016; Rumjit et al. 2021; Sadegh et al. 2021; Wang et al. 2021b). There was a more significant decrease in the peak intensity of MBC at 1100-1700 cm−1 after the reaction, which could indicate that these oxygen-containing functional groups play a crucial role in the catalytic degradation (Zhou et al. 2021). The removal capacity of MBC/PS for RhB could be related to the oxygen functional groups (-OH and C = O) in MBC (Xu et al. 2023; Yan et al. 2023).

Evaluation of MBC as the persulfate activator

Fig. 5a compared the removal of RhB by the MBC and MR-1 strains in different systems. It can be observed that 91.7% of RhB could be effectively degraded with the MBC/PS system. However, pure MR-1 almost had no degradation effect and only can remove 50.2% of RhB with PS. The degradation efficiency can be increased by 47.4% with MBC/PS rather than with MR-1/PS. As can be known from Table 1, the conventional ways for using microorganisms to degrade organic pollutants are pure bacteria, bacterial consortia, bacterial film, or bio-electrochemical systems. However, complex reaction systems, rather low degradation efficiency, or a relatively long time consumption of the above ways stimulate some new means to utilize microorganisms. In this work, the MBC was prepared as the PS activator with carbonization of bacteria. Higher degradation efficiency and less degradation time can be achieved with MBC/PS than with MR-1. The oxygen-containing functional groups on the surface of BC such as hydroxyl and carboxyl groups can effectively activate S2O82− to produce SO4•− (Oh and Nguyen 2022). Furthermore, •OH was also produced due to the hydrolysis of SO4•−. In this work, the pore structure, high N content, and high C = O/C-O ratio of the MBC can provide more catalytic active sites to contribute to the catalytic effect. Therefore, MBC is an effective PS activator that can enhance the ability of PS to remove RhB.

Fig. 5
figure 5

Degradation of RhB in different systems (a) and the effect of catalyst dosage (b), PS dosage (c), initial pH on RhB removal (C/C0) by MBC/PS (d), and the reusability of MBC (e)

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Table 1 Comparison of the degradation of organic pollutants by microorganisms in different reaction systems
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The effect of MBC addition, PS concentration, and initial pH on RhB degradation was assessed in Fig. 5b, d. As shown in Fig. 5b, the degradation efficiency increases with the addition of MBC. One hundred percent of RhB degradation can be achieved with the addition of 0.8 g/L MBC. The kobs reaction rate constant was increased from 0.0046 to 0.0143 min−1, which means that the increase of the catalyst concentration provided more active sites for PS activation (Table 2). PS concentrations also had a significant effect on RhB degradation (Fig. 5c). When the concentration of PS was increased by four times, the removal rate of RhB could be increased by 41.9%. This means that sufficient amount of SO4•− and •OH need to be produced with the appropriate amount of PS to oxidize and degrade RhB. Initial pH is also usually an important factor in degradation systems. Significant effect of pH values (pH = 3-11) on RhB removal efficiency can be observed in Fig. 5d. Under acidic and neutral conditions, the removal of RhB remained stable at around 88.0% with no obvious changes. However, the removal effect was greatly reduced in strongly alkaline conditions (pH = 11). Such differences may be due to electrostatic adsorption (Shi et al. 2023; Yang et al. 2023). BC has a positively charged surface in acidic solutions, which electrostatically adsorbs the negative ions of PS (S2O82−) and readily accesses the surface of the material, enabling effective activation. On the contrary, under alkaline conditions, BC shows more negative charge sites, and the caused electrostatic repulsion may limit its degradation rate. The above experiments show that MBC/PS can effectively degrade RhB over a wide pH range, which also indicates that the degradation reaction conditions are mild and economical and no extra strong acids or alkali are needed.

Table 2 First-order kinetic parameters for degradation of MBC dosage and PS concentration
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The reusability and stability of the catalyst MBC were verified by recycling experiments in conjunction with the practical application of the catalyst (Fig. 5e). After five cycles, it was observed that the removal of RhB decreased by 18.56%, which may be due to the reduction of active sites on the catalyst surface by cleaning and drying processes. In addition, the characterization of the MBC shows that there was no significant change before and after the reaction, which indicates that the material has good structural stability.

Mechanism of persulfate activation by MBC

In general, the oxidation capacity of the catalyst/PS may be ascribed to the generation of free radicals or non-radical active species. Typically, the •OH and SO4•− were usually regarded as the two major reactants for PS activation by metal-free catalysts. In this work, MeOH, TBA, and NaN3 were used to investigate the active species of the MBC/PS system. MeOH was highly reactive towards •OH and SO4•− and could quench both radicals efficiently at different reaction rates (kSO4•−  = 1.1 × 107 M−1 s−1, k•OH = 9.7 × 108 M−1 s−1) (Guo et al. 2021; He et al. 2021; Wu et al. 2021a; Zhou et al. 2020; Zhu et al. 2018a). TBA can only be used as •OH quencher with a reaction rate of 6 × 108 M−1 s−1, (Hu et al. 2017; Liu et al. 2021; Wu et al. 2021a). Known from Fig. 6a-b, the removal of RhB was decreased by 23.9% and 31.9% after the addition of MeOH and TBA, respectively, which can indicate that both SO4•− and •OH radicals play a role in the MBC/PS system. However, the inhibition effect of MeOH (kobs−2 M = 0.0041 min−1) was weaker than that of TBA (kobs−2 M = 0.0021 min−1) (Table 3), which can confirm that the effect of •OH is more significant than that of SO4•−. The above results can be explained as follows: the compensation effect of SO4•− produced from PS by CH2OH• on the degradation efficiency; the affinity of TBA with MBC to prevent from the entry of PS to MBC (Liu et al. 2022a; Ren et al. 2021). Furthermore, it can be found in Fig. 6a-b that MeOH and TBA cannot completely quench the reaction, suggesting that there may be other active species attributed to the RhB removal. NaN3 was typically used to capture singlet oxygen (1O2) (k = 1.2 × 108 M−1 s−1) (Xu et al. 2020), which is the typical active substance in the non-radical pathway. As observed in Fig. 6c, the degradation rate of RhB showed a significant decrease with increasing NaN3 concentration. 2 M NaN3 could inhibit the degradation of 46.0% RhB, indicating that 1O2 also played a significant role in RhB degradation by the MBC/PS system.

Fig. 6
figure 6

Effects of free radical inhibitor MeOH (a), TBA (b), NaN3 (c) on the degradation of RhB by PS catalyzed with MBC and the EPR spectra of •OH and SO4•− (d) and 1O2 (e) signals in the MBC/PS system

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Table 3 First-order kinetic parameters for degradation of different quenching agents
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To further demonstrate the contribution of the active species in the MBC/PS system, an EPR test was performed. •OH or SO4•− can form stable adducts with DMPO, and 1O2 can be detected by reacting rapidly with TEMP to form TEMPO+ radicals (Wang et al. 2023; Wu et al. 2022b, 2022d). In Fig. 6e, a quadruple peak with a relative intensity ratio of 1:2:2:1 for DMPO-•OH and a six-line peak with a relative intensity ratio of 1:1:1:1:1:1 for the DMPO-SO4•− adduct can be observed (Wu et al. 2020). Meanwhile, in Fig. 6f, the characteristic signals with the ratio of 1:1:1 for triplet peak of TEMP-1O2 can be observed (Huang et al. 2023). The results were also verified with the quenching experiments, which demonstrated that the MBC/PS system could indeed catalyze the generation of •OH, SO4•−, and 1O2 from activated PS by the quenching experiments and the EPR measurements. Based on the above experimental results, a more reasonable schematic of MBC activated PS was proposed, as shown in Scheme 1.

Scheme 1
scheme 1

Schematic representation of the mechanism of MBC activation of persulfate

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Conclusion

In this study, we employed Shewanella oneidensis MR-1 for the first time as a raw material for the preparation of biochar for the degradation of RhB by activated PS. Characterization techniques such as SEM, BET, XRD, XPS, and FTIR were used to examine the morphological structure and chemical content of MBC. Meanwhile, by comparing the degradation effects of pure strain MR-1 and MBC, it was discovered that the degradation effect of RhB was significantly improved after the carbonization of the bacterium, proving the high catalytic activity of the MBC material. MBC exhibited good stability and high catalytic action in a wide pH range. The quenching experiments and EPR tests indicated that •OH, SO4•− and 1O2 play an important role in the MBC/PS system. This study provided a new simple, efficient, and economical catalyst for the activation of PS, and also brings a new perspective on the resource utilization of bacteria.